Field of the Invention
The present invention relates to a method for producing a surface-treated glass fiber film and a flexible fiber substrate.
Description of the Related Art
With remarkable progress of digital technological, major electronic devices such as personal computers and mobile phones have been thinned, miniaturized and advanced. For example, high-density mounting, thinning and miniaturizing is required for a printed substrate as a representative component thereof. To meet this requirement, improvement in property of a glass fiber film, as an essential component of a printed substrate, is being strongly desired. Also, higher speed and frequency of computers, mobile phones, communications infrastructures and other devices have been developed. Accordingly, a demand for a glass fiber film used in a printed wiring substrate is to be a low-dielectric material for improving transmission loss. The material having low thermal expansion and high tensile rigidity is also strongly required. Due to further requirement for thinning and miniaturizing on a component, development of a thinner glass fiber film has earnestly been required.
As shown in recent semiconductor package for mobile devices in particular, a demand for a printed wiring substrate is increasing according to high-density mounting, thinning and miniaturizing, and higher performance of a semiconductor package. For example, in order to prevent a warp of a package that has been mounted, a substrate material having a lower linear expansion is required. To meet this requirement, conventional technologies introduce a laminate substrate obtained by impregnating a glass fiber with an organic resin composition having a high content of an inorganic filler. However, a high viscosity of a resin composition causes unfastening or twisting of a glass fiber, resulting in impaired uniformity of a substrate and a warp of a package from intrinsic stress.
Some prior arts, such as those disclosed in the following Patent Documents, describe a glass fiber film.
Patent Document 1 discloses a treatment solution for a glass fiber consisting of a mixture of alkoxy silane having no functional group or a hydrolyzed condensate thereof or both thereof, and alkoxy silane having a functional group or a hydrolyzed condensate thereof or both thereof, using alcohol as a solvent. The glass fiber using the treatment solution shows improvement in film-forming property, weather resistance and water resistance.
Patent Document 2 discloses a transparent film formed by impregnating a substrate of a glass fiber surface-treated with an acryloxy coupling agent with an epoxy resin as a transparent resin composition and curing the same. The transparent film is excellent in transparency and heat resistance, and low in retardation.
Patent Document 3 discloses a glass fiber film for a printed wiring substrate, using a sizing agent for a glass fiber containing a film-forming component and a silane coupling agent, wherein the film-forming component is a water-soluble urethane or a water-soluble epoxy resin or both thereof, and the attached ratio of the sizing agent is in the range of 0.05% to 0.4%. The glass fiber film treated with the sizing agent demonstrates improvement in migration resistance.
In addition, Patent Document 4 discloses a sizing agent for a glass fiber consisting of an acetylene glycol surfactant, a film forming agent, and a silane coupling agent. Illustrative example of the film forming agent includes a urethane resin, an acrylic resin, an epoxy resin, and a polyester resin. The glass fiber treated with the sizing agent shows improvement in wettability resistance and sizing property.
As described above, while properties such as heat resistance and weather resistance to a glass fiber improved, strength, flexibility, surface homogeneity, and dimensional stability of the film produced therefrom are insufficiently assured.
Patent Document 5 discloses a surface-treated glass fiber film, wherein the attached amount of a silane coupling agent was reduced to 0.8 to 2.0×10−5 mol/m2 in order to improve electric insulation. The surface-treated glass fiber film demonstrates improvement in electric insulation.
Patent Document 6 discloses production of a prepreg using silicone oligomer, and employs a partially hydrolyzed condensate of alkoxy silane. The silicone oligomer is used to treat the prepreg, and the prepreg obtained shows improvement in drilling property and electric insulation.
Nevertheless, since the surface-treated glass fiber film disclosed in Patent Document 5 has a small attached amount of a silane coupling agent, properties such as heat resistance and dimensional stability are insufficiently assured.
The prepreg disclosed in Patent Document 6 is prone to thermal expansion and thus dimensional stability is insufficient. In addition, since flexibility is also insufficient, it is hard to use the prepreg as a flexible substrate.
Consequently, the above prior arts fail to provide a method for producing a surface-treated glass fiber film having high strength and excellent in flexibility, surface homogeneity, and dimensional stability, obtained by surface-treating a glass fiber film with a silane coupling agent, with less environmental impact.